Decarbonizing medical gases: the challenge of nitrous oxide (N2O)

How can we reduce the carbon footprint of hospitals?

JCP: Every sector of activity is called upon to reduce its carbon footprint, and the healthcare sector, including hospitals in particular, is no exception. The healthcare sector's climate footprint accounts for 4.4% of global net emissions, equivalent to 2 gigatons of carbon dioxide¹. If the healthcare sector were a country, it would be the fifth largest emitter on the planet¹. In France, 38% of greenhouse gas emissions from the healthcare sector are generated by hospitals². Medicines and medical gases are included in this percentage. Air Liquide Healthcare's approach has been to engage in discussions with healthcare professionals to define priorities for action. Very quickly, our attention turned to medical nitrous oxide, or N₂O. Although rarely employed, medical N₂O is used in anesthesia for operating rooms, mainly in pediatrics.

Why is it necessary to decarbonize medical nitrous oxide N₂O? Is this really a key issue in combating global warming?

JCP: According to hospitals, medical nitrous oxide accounts for a minimal proportion of volumes (less than 1%), but it contributes significantly to the carbon footprint of medical gases (>75%) in most cases. This imbalance is explained by its powerful global warming potential, which is 273 times greater than that of carbon dioxide (CO₂) over a 100-year period³. In other words, 1 kg of N₂O used is equivalent to 273 kg of CO₂. Furthermore, medical N₂O is not metabolized by the body after administration, so the gas exhaled by the patient also has an impact. You can see how medical N₂O is a powerful lever for reducing carbon footprints, and our work with hospital healthcare professionals will therefore focus on reducing its volumes.

In practice, medical nitrous oxide is distributed in hospitals through a dedicated network, with wall outlets allowing the gas to be released in the operating rooms. The major challenge lies in gas losses associated with its distribution through the network. Studies conducted in the United Kingdom⁴ and the United States⁵ have revealed that medical N₂O distribution networks in hospitals can have a loss rate of over 90%! Micro losses in the network ultimately represent a very significant volume compared to the volume actually used for the patient. Taking action on medical nitrous oxide distribution by limiting losses therefore enables hospitals to massively reduce their greenhouse gas emissions.

How can medical N₂O be decarbonized? What implementation solutions does Air Liquide Healthcare offer?

JCP: Air Liquide Healthcare is aligning itself with the recommendations of the French Society of Anesthesia and Intensive Care (SFAR) by assisting hospitals in implementing the shutdown of their medical N₂O distribution network and switching to the use of cylinders for residual uses.

In concrete terms, we have developed a number of pilot projects with partner hospitals, and based on the successful experience of these pilots, we have rolled out this approach to other establishments. With the pediatric department at Toulouse University Hospital, we began by confirming the hypothesis of reducing useful medical NO₂ consumption by using cylinders rather than network distribution. Estimates made in this pediatric department show a very significant saving in medical nitrous oxide. It is our responsibility to take a proactive approach to the environment while responding to current medical needs. Air Liquide Healthcare is also involved in a research project aimed at destroying the residual medical N₂O contained in cylinders.

What other projects is Air Liquide Healthcare working on to decarbonize medical gases and and help build a more sustainable healthcare system?

JCP: The decarbonization of medical gases is not limited to N₂O, even if, as we saw earlier, it is a gas that needs to be addressed as a priority. For medical gases in France, our strategy for carbon neutrality by 2050 is also based on other levers:

• Optimizing the use of MEOPA (equimolar mixture of oxygen and nitrous oxide) by recommending specific equipment to rationalize gas consumption.
• Supplying low-carbon gases: medical liquid oxygen and medical liquid nitrogen are the most commonly used gases in hospitals and therefore contribute to greenhouse gas emissions from medical gases. Their main impact results from the emission factor of the electricity used to produce them. Thus, using 100% renewable electricity can reduce the carbon footprint of oxygen by more than 70%⁶. Air Liquide Healthcare therefore follows a policy of purchasing electricity produced from renewable energy sources and offers hospitals the ECO ORIGIN^TM solution.

Key points to remember:

• The healthcare sector, and hospitals in particular, must contribute to the reduction of greenhouse gases.
• Medical nitrous oxide (N₂O) is a powerful greenhouse gas, accounting for 75% of the carbon footprint of medical gases despite its very low volume, less than 1%.
• Massive losses are observed in medical N₂O distribution networks, making it a priority target for action.
• The solution is to stop network distribution and replace it with cylinders.
• Pilot projects have shown massive reductions in medical N₂O emissions with this strategy, exceeding 90%!
• Beyond medical N₂O, Air Liquide Healthcare's approach to carbon neutrality includes optimizing the use of other gases (MEOPA) and supplying medical gases (oxygen and nitrogen) produced with low carbon emissions, thanks to the use of 100% renewable electricity.